There are several manufacturing processes where monitoring energy transfer from a source to a workpiece is highly desirable to achieve accurate solidification manufacturing process control and repeatability. Non-limiting examples of such processes include laser welding as well additive manufacturing, which may use a wide variety of energy input sources.
As is known in the art, electron beam, arc, and laser welding involves directing a directed energy heat source at the interface of mating parts to join the same together at said interface. Monitoring energy transfer to the parts is important as it directly impacts manufacturing characteristics and quality. In certain welding operations, cameras may be utilized to monitor weld bead geometry at the weld point.
Additive manufacturing, or AM, is increasingly being used to manufacture parts of relatively complex geometries. One contemporary AM example involves building up parts by consecutively layering a powder and heating each layer with a laser as it is laid. The directed energy melts the powder forming a melt pool which then fuses to the existing part. This solidification manufacturing process is known as a build, and is done iteratively until a three-dimensional part is formed. Materials used may be metals, plastics, ceramics, etc.
Monitoring and controlling the thermal characteristics of the laser and the part during a build is of critical importance as these thermal characteristics have a direct effect on various characteristics of the finished part, e.g. geometrical accuracy, material properties, residual stresses, etc. A common approach to monitoring such thermal characteristics is to monitor the melt pool size and reduce or increase the power input from the laser accordingly. While this approach has provided some positive results, it does not provide an in depth understanding of the thermal characteristics for controlling AM. Further, such melt pool monitoring typically measures only the build surface (as opposed to a solidification manufacturing process volume) with the use of relatively complex measurement componentry such as infrared cameras and/or sensors.
There is a need for a measurement system which not only provides highly accurate, precise measurement of the modeled active volumetric solidification manufacturing process zone thermal characteristics but also offers a real-time low cost turn-key solution. Such a measurement system would have applicability in any application where it is desirable to measure directed energy input, e.g. electron beam, arc, and laser, used in welding, additive manufacturing, etc. The invention provides such a system. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.